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Owning Palette: Feature Extraction VIs

Installed With: Advanced Signal Processing Toolkit

Removes the trend from 1D signals by setting the approximation coefficients to zeroes. Wire data to the signal input to determine the polymorphic instance to use or manually select the instance.

Details  Example

Use the pull-down menu to select an instance of this VI.

Select an instance WA Detrend (waveform)WA Detrend (array)

WA Detrend (waveform)

	extension specifies the method to use to pad data at the borders of the input signal. The default is symmetric. The extension length is equal to the length of the wavelet filters. When you select the extension method, make the transition between the input signal and the padded data as smooth as possible because a smooth transition generates fewer large detail coefficients and enhances the efficiency of the signal representation. 0 zero padding—Uses zeroes to pad the input data. Watch for abrupt transitions between the padded zeroes and the input data, which causes large artifacts near the transition. 1 symmetric—Uses replications of the input data to pad the data, except that the VI left-flips the block at the input and right-flips the block at the end. 2 periodic—Adds a replication of the input data block before and another replication after the input data block to pad the data.
	signal specifies the input signal.
	trend level specifies the number of levels of the wavelet decomposition, which is approximately (1–trend level)×log2(Ls), where Ls is the signal length. The default is –1, which indicates that the VI estimates the optimal trend value according to the signal. trend level must be between 0 and 1. The larger the trend level, the closer the estimated trend matches the input signal.
	wavelet specifies the wavelet type to use for the discrete wavelet analysis. The default is db02. The options include two types: orthogonal (Haar, Daubechies (dbxx), Coiflets (coifx), Symmlets (symx)) and biorthogonal (FBI, Biorthogonal (biorx_x)), where x indicates the order of the wavelet. The higher the order, the smoother the wavelet. The orthogonal wavelets are not redundant and are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and are suitable for signal or image feature extraction. If you want to use other types of wavelets, do not wire this input. Instead, use the Wavelet Design Express VI to design the wavelet you want, bundle the resulting analysis and synthesis filters, and then wire them to the filter banks input.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	filter banks specifies the analysis filter banks and the synthesis filter banks for the wavelet you specify. If you specify a value for filter banks, the VI ignores the settings in the wavelet input. You can use the Wavelet Design Express VI to design the analysis filters and the corresponding synthesis filters. analysis filters specifies the coefficients of the lowpass analysis filters and the highpass analysis filters for the wavelet you specify. lowpass specifies the coefficients of the lowpass analysis filter, which the VI uses to compute the approximation coefficients. highpass specifies the coefficients of the highpass analysis filter, which the VI uses to compute the detail coefficients. synthesis filters specifies the coefficients of the lowpass synthesis filters and the highpass synthesis filters for the wavelet you specify. lowpass specifies the coefficients of the lowpass synthesis filter, which the VI uses to filter the interpolated approximation coefficients in the wavelet reconstruction. highpass specifies the coefficients of the highpass synthesis filter, which the VI uses to filter the interpolated detail coefficients in the wavelet reconstruction.
	detrended signal contains the signal without the trend.
	trend signal contains the residual trend of the signal.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

WA Detrend (array)

	extension specifies the method to use to pad data at the borders of the input signal. The default is symmetric. The extension length is equal to the length of the wavelet filters. When you select the extension method, make the transition between the input signal and the padded data as smooth as possible because a smooth transition generates fewer large detail coefficients and enhances the efficiency of the signal representation. 0 zero padding—Uses zeroes to pad the input data. Watch for abrupt transitions between the padded zeroes and the input data, which causes large artifacts near the transition. 1 symmetric—Uses replications of the input data to pad the data, except that the VI left-flips the block at the input and right-flips the block at the end. 2 periodic—Adds a replication of the input data block before and another replication after the input data block to pad the data.
	signal specifies the input signal.
	trend level specifies the number of levels of the wavelet decomposition, which is approximately (1–trend level)×log2(Ls), where Ls is the signal length. The default is –1, which indicates that the VI estimates the optimal trend value according to the signal. trend level must be between 0 and 1. The larger the trend level, the closer the estimated trend matches the input signal.
	wavelet specifies the wavelet type to use for the discrete wavelet analysis. The default is db02. The options include two types: orthogonal (Haar, Daubechies (dbxx), Coiflets (coifx), Symmlets (symx)) and biorthogonal (FBI, Biorthogonal (biorx_x)), where x indicates the order of the wavelet. The higher the order, the smoother the wavelet. The orthogonal wavelets are not redundant and are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and are suitable for signal or image feature extraction. If you want to use other types of wavelets, do not wire this input. Instead, use the Wavelet Design Express VI to design the wavelet you want, bundle the resulting analysis and synthesis filters, and then wire them to the filter banks input.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	filter banks specifies the analysis filter banks and the synthesis filter banks for the wavelet you specify. If you specify a value for filter banks, the VI ignores the settings in the wavelet input. You can use the Wavelet Design Express VI to design the analysis filters and the corresponding synthesis filters. analysis filters specifies the coefficients of the lowpass analysis filters and the highpass analysis filters for the wavelet you specify. lowpass specifies the coefficients of the lowpass analysis filter, which the VI uses to compute the approximation coefficients. highpass specifies the coefficients of the highpass analysis filter, which the VI uses to compute the detail coefficients. synthesis filters specifies the coefficients of the lowpass synthesis filters and the highpass synthesis filters for the wavelet you specify. lowpass specifies the coefficients of the lowpass synthesis filter, which the VI uses to filter the interpolated approximation coefficients in the wavelet reconstruction. highpass specifies the coefficients of the highpass synthesis filter, which the VI uses to filter the interpolated detail coefficients in the wavelet reconstruction.
	detrended signal contains the signal without the trend.
	trend signal contains the residual trend of the signal.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

WA Detrend Details

The trend of the input signal is the slow-varying part of the signal that mainly contributes to the approximation coefficients. The VI applies the following steps to implement the detrend function.

1. Apply the discrete wavelet transform to the input signal.
2. Set the approximation coefficients to zeroes.
3. Reconstruct the signal based on all the detail coefficients.

Example

Refer to the Detrend and Trend Estimation VI in the labview\examples\Wavelet Analysis\WAGettingStarted.llb for an example of using the WA Detrend VI.